Exhaust aftertreatment systems are used to receive and treat exhaust gas generated by IC engines. Conventional exhaust gas aftertreatment systems include any of several different components to reduce the levels of harmful exhaust emissions present in exhaust gas. For example, certain exhaust aftertreatment systems for diesel-powered IC engines include a selective catalytic reduction (SCR) catalyst configured to convert NOx (NO and NO2 in some fraction) into harmless nitrogen gas (N2) and water vapor (H2O) in the presence of ammonia (NH3). Generally, in such conventional aftertreatment systems, an exhaust reductant, (e.g., a diesel exhaust fluid such as urea) is injected into the aftertreatment system to provide a source of ammonia, and mixed with the exhaust gas to partially reduce the NOx gases.
The reduction byproducts of the exhaust gas are then fluidically communicated to the catalyst included in the SCR aftertreatment system to decompose substantially all of the NOx gases into relatively harmless byproducts which are expelled out of such conventional SCR aftertreatment systems. The percentage of the NOx gases or other constituents in a given volume of the exhaust gas which are decomposed into the harmless byproducts after flowing through the aftertreatment system depends on a catalytic efficiency of the catalyst. The higher the catalytic efficiency, the higher the percentage of NOx gases converted into harmless byproducts. Increasingly stringent emission requirements demand that the catalyst of the SCR system have higher catalytic efficiency to meet and exceed the emission requirements.